Importing customers database from a business to another

Hello,

I have created a business with the wrong default currency. The support here told this is irreversible.

Then I created another business with the right currency.

Now I need to import the customers from the first business to the other.

The export process worked well, but when I switch to the other account (0 customers) and try to import the cvs file I get this error:
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All of your contacts already exist in Clear Books.
Customer is a required field.
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I tried to remove both businesses and create a clean new one, but the problem persist. I can't import the customers data.

Please advise.

thanks.